Hyundai Motor Co is recalling more than 140,000 Tucson crossover utility vehicles because the air bag assembly may come loose from its mounting on the steering wheel, according to documents filed with U.S. auto safety regulators.

The South Korean automaker said the recall affects 137,500 Tucsons in the United States and 3,500 in Puerto Rico, from model years 2011 to 2014, according to documents filed with the National Highway Traffic Safety Administration.

Hyundai said that during assembly, it is possible the two bolts attaching the driver's air bag module to the steering wheel may not have been properly tightened. It said the air bag module might become detached from the steering wheel, which could result in injury in the event of a crash.

There have been no reports of accidents or injuries as a result of the defect, the automaker said.

NHTSA said Hyundai will notify car owners of the recall, which is expected to begin at the end of June, and dealers will inspect and tighten the bolts free of charge.